Currently, what other unit (from other books), with character, buffs etc, can take on a big unit of bloodletters, with a Herald on jugger in the front?

A better question maybe, is what character can take the charge from a Herald on Jugger and win?

Dark elf Death star. It always strikes first, hates you at all times, and the lord is nigh invulnerable to your high strength attacks, so he will tie you down in a challenge. Or that same lord on a dragon.

Funny enough, a Giant (hordes of chaos) with mark of slanesh can ruin your day. A Hellpit abomination (skaven) will also do the trick. A steam tank at ramming speed. An archlector of sigmar on a waraltar with a VHS will also do very well. A dwarf lord on shield bearers in full defensive regalia has strong chances. A treeman with Annoyance of netlings will make you work for it.. Chaos lord on a dragon or otherwise, with armour of damnation will give you a hard time.

If you give your herald of Khorne the Firestorm Blade to increase his Str and make his attacks flaming (or use Skulltaker on Juggernaut), Dragon Princes (i think their names are) from the High Elves are enough... Because they are immune to fire. Else you could beat it with a unit of Daemonettes (ASF) or Plaguebearers (because of Regeneration).

There are actually alot of units who can defeat a unit of Bloodletters with their Herald, they are really strong of course, but they just have 1 Attack (the daemonettes have 2 each). The only good thing is Hatred I suppose and they're supposed to be the best melee menace as core unit. I personally have never used them, they are good in great numbers using the Standard of Chaos Glory.